Circuit arrangement for multiple-unit tubes



Dec. 29, 1931. o w 1,838,855

CIRCUIT ARRANGEMENT FOR MULTIPLE UNIT TUBES Filed Jan. 17, 1927 12mm HUM! INVENTOR SIEGMUND. LOEWE TTORNEY Patented Dec. 29, 1931 UNITED STATES PATENT {OFFICE SIEGMUND LOEWE, OF BERLIN, FRIEDENAU, GERMANY, ASSIGNOR TO RADIO CORPORA- TION OF AIVIERIC'A, A CORPORATION OF DELAWARE CIRCUIT ARRANGEMENT Fo ULTIrLE-UNIT TUBES Application filed January 1'7, 1927, Serial No.

This invention relates to multiple unit tubes. The term multiple-unit tubes is used herein for vacuum tubes in which several electrode systems each comprising a cathode, one or several grids, and an anode together with coupling means such as high-ohmic resistances, coupling condensers, and the like, are assembled inside one and the same vacu-; ous space. Usually such tubes are designed to contain two electrode systems which are coupled by a high-ohmic resistance by way of a coupling condenser with grid leak resistance. The diflicultyencountered in the operation of these new tubes resides in that, due to the effective aperiodic radio frequency amplification, also in the case of shorter waves, freedom from disturbance that is, selectivity is rendered less: easy. However, by the ways and means hereinafter to be disclosed it is. feasible to fully utilize the tube together with a high degree of selectivity. The general idea underlying the circuit arrangement in question is as follows:

The radio frequency double amplifier tube, by special means, is caused to assume a working state so that a reduction'in damping is produced in the circuits arranged ahead of, or in series with the tube. Additional circuits which serve for rendering the reception perceptible may then be connected without any special precautionary measures being required since, by virtue of the reduction of damping, a definite frequency will be favored, and this particular wave will be preferably received in the subsequent circuits.

In the accompanying drawings Figure 1 shows an arrangement wherein such a reduction in damping is realized and,

Figure 2 shows a modified arrangeme t which makes use of back coupling to, t in reducing damping effects.

The receiving arrangement will be hereinafter described in more detail by reference to Figure 1 showing an embodiment of the idea by way of example. Referring to Figure 1, 1 denotes an antenna, either tuned or untamed which works inductively upon the tuned circuit 2 connected ahead of the twosystem tube. Circuit 2' is unitedwith the 161,505, and in Germany February 15, 1926.

control grid 3 of thetwo-system tube 4, the

Now, according to the invention, the output circuit of tube 4 contains means adapted to produce reduction in damping, for instance, an inductance coil 14 which may comprise either aconstant or a variable iron core 15.

The said inductance impedance may consist also of an ordmary telephone receiver, a plan that may beof advantage for tuning purposes.

If the said in'ipedance is adequately high,

it is found that the systeni so far described is caused to start oscillations at its natural frequency, to be more precise, at a frequency which is essentially governed by the factors or' quantities of the tuning circuits 1, "2 connected in serieswith and ahead of the doublesystem tube. Now, the best plan is not'to push the reduction in damping to a point where self-oscillation is occasioned, indeed, arrangements should be so made as to remain below that particular point by diminishing the inductance or else by connecting a condenser in j parallel thereto. N ow, the coupling of additional amplifier systems is effected in a manner so that in parallel to the means adapted to produce reduction in damping, there is connected a preferably variable condenser 16 by way of a' coupler coil 17. The coupling of t 1e subsequent circuitsis effected by way of the oscillation circuit 18'Wl1lCl1 is likewise tuned and which. for instance, is connected with the input end of the resistance-coupled low frequency amplifier with rectifier action.

In the figures is shown atwo-stage amplifier of this kind. x 19 and 20 are two resistancecoupled amplifier tubeswhich worlr'upon a telephone receiver orloud-s Jeaker 21. For practical purposes,'a three stage resistance coupled receiver or what is known as a local receiver with loud-speaker end-stage is ordinarily employed.

The advantages offered by the arrangement as hereinbefore described are as follows: By virtue of the variable inductance 15 and of the reduction in damping produced thereby, there is obtained a very great increase in selectivity of the arrangement 1, 2 and at. The alternating current potential set up in the inductance is fed to the coil 17 by Way of the condenser 16. Between coils 17 and 18 there exists also a preferably variable coupling. T he condenser 16 does not necessarily have to be variable. But the COmb1IlEL tion comprising 16 and 17 may be so chosen that it will be tuned to the incoming Wave so that no high frequency alternating potential is able to arise across the terminals of the inductance 1 1. In the presence of such condition, no maximum current of the desired frequency can flow through the coil 14. By means of the total or partial elimination or neutralization of the alternating potential in the inductance 14 thus obtained, there is produced at the same time a reduction in damping. Indeed, it is thus feasible to regulate at will the damping reduction also by the circuit 16, 17, which, as stated before, need not necessarily be tuned.

The circuit arrangement described above is also suited for the use of a separate external back-coupling. Such an arrangement has been shown in Figure 2 wherein a regenerative loop has been provided. The adopt-ion and provision of such a separate regenerative coupling may be of advantage Whenever the receiving apparatus is to be made ei'licient for very large wave ranges.

It may also be mentioned that instead of the inductance 14, 15, also a purely ohmic resistance could be employed, the same being of the variable type so as to be able to regulate the amount of reduction in damping to be obtained.

Another point to be mentioned is that, of course, the heating and plate batteries indicated in Figure 1 may be combined.

Having thus described my invention, I claim:

1. A. radio signalling system comprising a multiple unit tube means for feeding back energy from its last stage to its first stage of amplification, a choke coil in the output circuit of said tube, a series tuned radio frequency circuit in parallel with said choke coil, and a second circuit inductively coupled to said tuned circuit.

2. A radio signalling system. comprising means for producing a plurality of stages of radio frequency amplification, means for feeding back energy from the output of one of said stages to a preceding stage, a choke coil in the output circuit of one of the stages, a series tuned circuit connected across said choke coil and a second circuit inductively couped to said tuned circuit.

SIEGMUND LOEVVE. 

